Nanospheres can repair spinal cord injuries

Emma Woollacott, 9th November 2009

Researchers at Purdue University have found they can repair damaged nerve fibers in spinal cord injuries by injecting nanospheres into the blood shortly after an accident, raising hopes of a new treatment for paralysis.

The synthetic 'copolymer micelles' are drug-delivery spheres about 60 nanometers in diameter which have been used previously to deliver cancer medication. But the researchers have discovered that the micelles themselves can repair damaged axons, the fibers that transmit electrical impulses in the spinal cord.

"That was a very surprising discovery," said Ji-Xin Cheng, an associate professor in the Weldon School of Biomedical Engineering and Department of Chemistry. "Micelles have been used for 30 years as drug-delivery vehicles in research, but no one has ever used them directly as a medicine."

The micelles might be used instead of more conventional "membrane sealing agents," including polyethylene glycol (PEG), which makes up the outer shell of the micelles. Because of the nanoscale size and polyethylene glycol shell of the micelles, they aren't quickly filtered by the kidney or captured by the liver - so they can remain in the bloodstream long enough to circulate to damaged tissues.

"With the micelles, you need only about 1/100,000th the concentration of regular polyethylene glycol," Cheng said.

The experiment mimicked a traumatic spinal cord injury. Without the micelles treatment, about 18 percent of axons recovered in a segment of damaged spinal cord; the micelles treatment boosted this to about 60 percent.

The researchers also tracked dyed micelles in rats, to show they could be successfully delivered to injury sites. Micelles-treated animals recovered the coordinated control of all four limbs, whereas animals treated with conventional polyethylene glycol did not.

Next, the researchers want to learn about the specific mechanisms that enable the micelles to restore function to damaged nerve cells.